Miniature, remote-head cameras are commonly used in endoscopy and other areas of minimally-invasive surgery. A solid-state imaging sensor is fixed in the distal end of an endoscope, along with suitable imaging optics and an illumination source, in order to capture images within body cavities and passageways. In general it is desirable to reduce the endoscope diameter and at the same time to improve the image quality obtained from the distal-end camera head. These two objectives are often mutually contradictory, since increasing the resolution of the sensor generally requires increasing its size, which leads to increasing the diameter of the endoscope.
A wide variety of distal-end camera heads have been described in the patent literature, based mainly on integration of the sensor, typically a CCD-based sensor, with suitable miniature optics. Some exemplary camera head designs are described in U.S. Pat. Nos. 4,604,992, 4,491,865, 4,746,203, 4,720,178, 5,166,787, 4,803,562, and 5,594,497. Some systems and methods for reducing the overall dimensions of the distal end of an endoscope containing an image sensor are described in U.S. Pat. Nos. 5,929,901, 5,986,693, 6,043,839, 5,376,960, and 4,819,065, and in U.S. Patent Application Publication No. 2001/0031912 A1. One technique that has been suggested for reducing endoscope diameter is to orient the image sensor in a plane that is parallel to the axis of the imaging optics, rather than perpendicular to the plane as in conventional optical designs. Implementations of this technique are described in U.S. Pat. Nos. 4,692,608, 4,646,721 and 4,986,642 and in the above-mentioned U.S. Patent Application Publication 2001/0031912 A1. The disclosures of all the above publications are incorporated herein by reference.
Although most endoscopes provide the user with a single, two-dimensional image, endoscopes with three-dimensional imaging capability are also known in the art. For example, endoscopes that generate stereoscopic images by using two different optical paths are described in U.S. Pat. Nos. 5,944,655, 5,222,477, 4,651,201, 5,191,203, 5,122,650, 5,471,237, 5,673,147, 6,139,490, and 5,603,687, whose disclosures are likewise incorporated herein by reference.
Endoscopes typically use an external illumination source to provide radiation to the distal end of the endoscope via fiber optics. On the other hand, some endoscopes employ illumination devices integrated within the endoscope itself, either at the distal end or at the proximal end of the endoscope. For example, the use of Light Emitting Diodes (LEDs) for this purpose is described in U.S. Pat. Nos. 6,318,887, 6,331,156, 6,260,994, 6,371,907, and 6,340,868, whose disclosures are incorporated herein by reference.